Cytology
A Tour of The Cell
How cells are studied

Microscopy

Cell Fractionation
Microscopy


Light microscope enables us
to see the overall shape and
structure of a cell
light microscope (LM)


1600s
Resolution = 0.2m


leaf of a live plant
electron microscope (EM)



1950s
TEM, SEM
Resolution = 0.2nm

fish gills
Cell Fractionation

Isolates organelles to study their function

Isolation is accomplished by centrifugation

Reductionist approach
Cell Size

Cell size and shape is related
to its function

Prokaryotic
 most are 1-10 m

Eukaryotic
 10-100 m
 RBC 7.5µm
 WBC 10-12µm
 ovum 170µm
Contributions to the Cell

Robert Hooke (1665)



Antoine van Leeuwenhoek (1600's)




first "microscope"
first to see living cells
magnified 300X
Matthias Schleiden (1838)


coined ‘cell’
first to see cells (cork cells, 30x)
plants are made of living cells
Theodor Schwann (1839)

animals are made of living cells
Principles of the Cell Theory

all organisms are made of cells

cells are the smallest living things

life is a continuous line of descent from early
cells

cells come from other cells
Prokaryotic Cells

Ubiquitous (air, water, soil, surfaces)

3.5 billion years

6300 species recognized

400K to 4 M estimated

most numerous


size - 1-10 m
largest 0.5 mm
Prokaryotic Cell Domains

Archaea

inhabit extreme environments




hot springs
salt ponds
acidic conditions
Bacteria

larger group
Archaea & Bacteria

Different




Structurally (cell walls)
Biochemically (initiator a.a.)
Physiologically (histones)
Archaea



w/ introns (protein synthesis)
not inhibited by antibiotics
more like eukaryotes
A Prokaryotic Cell
Basic Cell Shapes

coccus - sphere

bacillus - rod

spirillum - spiral
Evolution of Eukaryotes

Prokaryotes evolved 3.5 billion years ago

Eukaryotes evolved 1.5 billion years ago

prokaryote
eukaryote
Animal Cell
Plant Cell
Plasma Membrane


selectively permeable
support
Cell Wall

NOT found in animal cells

Functions
 protects, supports,
shapes the cell

Composition
 varies from species to
species
 cellulose in Plantae
 chitin in Fungi
Nucleus





Function: control
center
 Nuclear envelope
 Nuclear pores
 Contains DNA
DNA synthesis
Nucleolus
 Synthesizes ribosomal
subunits
Nuclear matrix
Largest animal cell organelle
Ribosomes






Function: makes proteins
Made of rRNA + proteins
Free (cytosol), proteins function in the cytoplasm
Bound to the ER, proteins are for organelles in the cell or
export
two subunits (large and small)
synthesized at nucleolus
Endoplasmic reticulum (ER)


divides cells into compartments
forms vesicles

rough ER (RER)


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Synthesizes protein
smooth ER (SER)
diverse functions


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Synthesizes lipids
metabolizes carbohydrates
Detoxifies
stores calcium
Golgi Apparatus

flat stacks of membranes (cisternae)


function: collects, modifies, packages, transports
Secretion of cell products


cis face
trans face
Lysosomes
(animal cells only)



Golgi derived
Hydrolytic enzymes
function:



breakdown of macromolecules
destroy bacteria
recycle damaged organelles (autophagy)


phagocytosis
function in embryonic development in animals
Tay-Sachs lacks them
autophagy
Vacuoles

food vacuoles (animal cells)

contractile vacuoles (Protists)

central vacuoles (plant cells)
ibrary.thinkquest.org/3564/gallery.html
Central Vacuole (plant cells only)



Surrounded by a membrane known as tonoplast
Largest plant cell organelle
Function



Similar to lysosomes in animal cells
Storage (organic compounds, ions, water, pigments)
Hydrolyzing (breakdown molecules)
vacuole
tonoplast
nucleus
chloroplast
DNA-Containing Organelles
(energy transformers)

These organelles resemble bacteria

endosymbiotic hypothesis


chloroplasts (plant cells only)
mitochondria
Mitochondria

Contain


small ribosomes
circular DNA (mitochondrial DNA)
1-10 m long
 self-replicating
 function: energy production (ATP)


Membranes



outer smooth membrane
inner folded membrane, cristae
Compartments


intermembrane space
mitochondrial matrix
Plastids

Closely related plant organelles

amyloplast - colorless, store starch

chromoplast - with xanthophylls and carotenes

chloroplast - with chlorophylls
Chloroplasts




Contain small ribosomes and circular DNA
2 m tall by 5 µm long
self-replicating
function: photosynthesis
Peroxisomes

contain enzymes

detoxify and form H2O2 (hydrogen peroxide), as
intermediate product, then forms water

breakdown fats (fatty acids)

bounded by a single membrane

split in two when they reach a certain
size
Cytoskeleton

Functions:




support
maintain cell's shape
movement
3 types of fibers



microtubules
microfilaments
intermediate filaments
Centrioles

function: movement of
chromosomes

found in pairs, at right angles

9 sets of triplet microtubules
in a ring

location: centrosome
Flagella and Cilia

Function: movement

9 + 2 pattern microtubular
arrangement

9 doublets + a pair at center
Flagella
undulate
one or few
Giardia
Cilia
beat in one direction
numerous
Inside your trachea
Extra cellular Matrix (ECM)


only in animal cells
Functions


Support, adhesion, movement, regulation
Composition

varies




Glycoproteins
Collagen
Proteoglycans
Fibronectin
Physical Connections

Plant cells


Plasmodesmata
Animal cells, 3 main types



Desmosomes (anchoring) junction
Tight (organizing) junctions
Gap (communicating) junctions
Plasmodesmata

Plant cells

Plasmodesma (singular) plasmodesmata (plural)
Animal Cells- Junctions
Tight
(organizing)
Desmosomes
(anchoring)
channels
extracellular matrix
Gap junction
(communication)
Tight junctions

membranes of adjacent cells are fused, forming continuous
belts around cells

prevents leakage of extracellular fluid
tight junction
Desmosomes

fasten cells together into strong sheets, much like rivets

Intermediate filaments of keratin reinforce desmosomes
Gap junctions

Channels between adjacent cells

Special membrane proteins surround these pores

Small molecules can pass through




Salt
Ions
Sugar
water
Activity
A. Cell wall
B. Plasma membranes
C. Nucleus
D. Ribosomes
E. Rough ER
F. Smooth ER
G. Lysosomes
H. Peroxisomes
I. Vacuoles
J. Cytoskeleton
K. Centrioles
L. Flagella and Cilia
M. Chloroplast
N. Mitochondrion
O. Golgi
power house
protection, support, shapes cell
photosynthesis
movement
houses DNA
protection and support
synthesis of lipids, detoxification
collect, modify, package and transport
synthesis of protein
synthesis and transport of protein
detoxify and brake down of lipids
movement of chromosomes
storage and brake down of molecules
support, cell shape and cell movement
contains enzymes of various functions
answers
A. Cell wall
B. Plasma membranes
C. Nucleus
D. Ribosomes
E. Rough ER
F. Smooth ER
G. Lysosomes
H. Peroxisomes
I. Vacuoles
J. Cytoskeleton
K. Centrioles
L. Flagella and Cilia
M. Chloroplast
N. Mitochondrion
O. Golgi
The End
power house N
protection, support, shapes cell A
photosynthesis M
movement L
houses DNA C
protection and support B
synthesis of lipids, detoxification F
collect, modify, package and transport O
synthesis of protein D
synthesis and transport of protein E
detoxify and brake down of lipids H
movement of chromosomes K
storage and brake down of molecules I
support, cell shape and cell movement J
contains enzymes of various functions G